Rotational spectrum, hyperfine spectrum and structure of lithium isocyanide

Abstract

The rotational spectrum of LiNC has been measured for the first time. We succeeded in producing a supersome molecular beam (= 1% LiNC in Ar). The molecular-beam electric-resonance technique has been employed to obtain high-resolution microwave spectra. Two rotational transitions (J = 1 → 0 and J = 2 → 1) of 7LiNC in the ground vibrational state were observed. The hyperfine structure was resolved and identified with the help of microwave-microwave double resonance. The rotational constants B0 and D0 and the hyperfine coupling constants eQq(Li), eQq(N), and c(Li) could be deduced. The J = 1 → 0 rotational transition of 6LiNC was observed in natural abundance. From this we conclude that LiNC has a linear isocyanide structure. The results for the effective structural parameters are: rLiN = 1.760 Å, and rNC = 1.168 Å. We did not observe transitions in excited vibrational states or from LiCN. The agreement between the experimental results and recent ab initio calculations is good.